The following section is presented for informational purposes only. The inclusion of material in this section should not be considered to be an admission that such material is prior art to the present application.
Electronic devices are used in a wide range of conditions including desert and arctic environments. In many cases, the energy storage device utilized in these electronic devices are rechargeable batteries formed of one or more cells. Because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current (which may vary with time), the allowable terminal voltage of the battery, and environmental conditions, such as temperature.
In particular, the permanent capacity of rechargeable batteries typically used as a power source may vary widely with temperature, from 100% at moderate temperatures to possibly 0% at temperature extremes, especially cold temperatures. In addition to environmental conditions, the permanent capacity of batteries may decay over their operational life with aging or charge/discharge cycling. This decay may be accelerated even more by the environmental conditions. Further, the acceleration of decay may itself be a function of deployment temperature, such that batteries aged under a set of environmental conditions may experience different capacity decay if subsequent usage is at moderate temperatures versus usage at extreme temperatures. Alterations in operational temperatures that result in capacity decay are referred to as thermal cycling decay. Thermal cycling decay is particularly prevalent when batteries are subjected to extreme cold temperatures common in the field of seismic exploration, which are often below −20° C. and may be as low as, if not below, −40° C.
Various techniques may be used for battery testing including battery burn-in testing during manufacturing, model simulation of capacity in extreme conditions, testing during charging at out-of-spec temperatures, testing for capacity remaining in down-hole oil field applications, and estimating capacity with temperature correction. Battery testing is routine during the product development cycle in mobile phone, laptop, and automotive fields. However, these techniques primarily focus on testing batteries within certain predetermined parameters or designed operational specifications, such as the cell discharge rate for which the battery is designed.
While the need for improved method of battery performance prediction may extend to many fields including automotive, aerospace, medical, consumer electronics, and anywhere a battery is used in remote or inaccessible locations such as satellites, remotely operated vehicles or snow machines, one field in particular where accurate performance predication is critical is the field of seismic exploration. In the extreme temperature environments common in seismic exploration, seismic data acquisition devices such as seismic recording units (RUs) may suffer unacceptable battery life in a given deployment, aging over time and multiple cycles, and combined effects, as well as potential mechanical stresses and irreversible chemical reactions that could cause a battery to fail to function safely or at all. Characterization of these effects is essential to predict the duration of batteries used, especially for planning purposes. This is particularly true since RUs utilized in these extreme conditions are typically sealed, with electronics, sensors and batteries built into the products. As such, batteries for these devices are not readily replaced, and the need to accurately predict performance is heightened. In any event, features of the corresponding RU's usage regime complicate testing of seismic batteries. For instance, the performance of an RU's battery may be impacted by the extremely low discharge rates common in RU devices. As a non-limiting example, these rates may be as low as a few mA or lower. On the one hand, the low rate allows usage scenarios unforeseen by mobile phone, laptop, and automotive battery pack makers, as well as the cell makers themselves. On the other hand, the low rate significantly extends the testing duration before useful results can be obtained.
There is a need for improved method of battery performance prediction and evaluation, particularly for battery performance prediction and evaluation outside standard operating parameters. Such prediction and evaluation should address a variety of usage regimes of batteries across a range of temperature, charge/discharge cycling, and discharge rates, especially for regimes of operation significantly beyond the original specification of the battery.